I have a Focus Test Fixture, how do I calibrate it?

June 12, 2024


Symptoms / Solutions:

The Focus test fixture can be calibrated using the Focus TRL calibration technique. The quality of this calibration technique depends on the quality of the VNA calibration performed prior to the FOCUS TRL calibration. The following steps describe the procedure to calibrate the test fixture.

Verify the accuracy of the VNA calibration.

Open the Focus Load pull explorer and click the Focus TRL Calibration button. This opens the Focus TRL/LRM calibration window.

Specify the working directory and select the calibration type as TRL calibration (default).

Connect the test fixture at the VNA calibration reference plane.

Adjust the movable section of the fixture so that a thru is established between the fixed input and the movable output sections.

Enter the length of the thru and click the S-parameter button to measure the S-parameters.

Insert the delay block between the input and the output blocks as shown below.

Enter the characteristic impedance of the delay section (default 50 Ω) and click the S-parameter button to measure the S-parameters.

Remove the delay section and leave the end of the input and the output sections open as shown below. If the short standards are used, connect them to the input and output sections.

Select the reflection type as open (default) and measure the S-parameters at port 1 and 2 as shown in figure 9.

Once the three standards are measured, click the Calculate button and this generates the S-parameter files for the input (CONA.S2P) and the output sections (CONB.S2P) of the test fixture.

Additional Information:

The Focus TRL calibration can also be performed in wizard mode by selecting the wizard option from the FOCUS TRL/LRM calibration window. The wizard mode guides the user through the step-by-step process of performing the TRL cal. Additional information can be found in the FDCS.Operation manual in \Focus Microwaves\Load Pull Explorer\Manuals

Keywords: Test fixture, TRL calibration

Last date modified: 06th March, 2017